1. Field of the Invention
The present invention relates to a mobile communication system, and more particularly to an apparatus and method for duplexing a high-speed processor board using a real-time operating system (RTOS) in a mobile communication system.
2. Background of the Related Art
Unlike a general computer system, a control system of a full electronic exchange requires a high-sensitivity fault tolerancy function and a real-time process. To meet demand, each exchange adopts various structures according to conditions. Most exchanges basically adopt a duplex method to perform fault tolerancy, and some of them adopt a load-sharing method in a multi-processor structure.
Generally speaking, there are two types of duplex methods: a synchronized duplex method (hot standby) and a synchronized duplex method (warm-or cold standby).
In the synchronized duplex method, an active device and a standby device are synchronized by a micro-level instance, instruction word-instance, or a program-process instance to operate simultaneously. Therefore, the synchronized duplex method is intended to recover from a fault condition as quickly as possible when it occurs.
In a system using a common processor such as a mobile communication exchange, the synchronized method of the instruction-word instance is considered undesirable because it exhibits such severe performance degradation that it can hardly be implemented. Also, the synchronized method of the program-process instance experiences performance degradation due to a software load, even though it has a little performance degradation. Especially, in a system using a parallel-process operating system, software overhead and overlapping become severe.
In an asynchronized duplex method, a standby processor is not initially operated, and subsequently starts an operation that has been performed by an active processor at a time when the active processor is in fault. There are at least two concerns in implementing the asynchronized duplex method: To maintain the same memory data in both the active device and the standby device (data consistency) and to quickly switch the standby device to perform a normal operation (continuous operation).
To solve such problems, in most switching systems, a data change in the operating active device is reflected using a counter device, standby device. This involves a first method, which transmits changed data of the active device to the standby device in message form, and a second method, which concurrently writes changed data into both the active device and the standby device. In the first method, performance degradation of hardware can be decreased but overhead of software is significant. Moreover, this overhead sharply increases as the amount of information transmission increases. In the second method, overhead of software is reduced but performance degradation takes place.
Generally, most second generation (2G) mobile communication systems including Digital Cellular Network (DCN), Personal Communication Service (PCS), and Wireless Local Loop (WLL), have adopted the second method for concurrently writing changed data into the active and standby devices.
More specifically in a 2G mobile communication system, a D channel is connected by hardware between two duplex processor boards, namely the active board and the standby board. Also, accessed contents of a local memory by a processor of the operating active board are also reflected in a memory of the standby board on a real-time basis through the D channel without software. Since memory contents of the standby board are equally changed when memory contents of the active board are changed, memory synchronization between the active board and standby board can be maintained when the active board is normally operated.
When a fault of the active board is detected, the active board takes over a controlling authority to the standby board. In this process, information of a Program Counter (PC) and contents of various registers are transmitted to the standby board. The standby board receives the controlling authority from the active board and subsequently starts the operation that has been performed by the active board, or that was being performed at the time the fault was detected.
In the duplex processor of the 2G mobile communication system operating according to the concurrent writing duplex method, since the memory contents of the standby board is already identical to that of the active board, when a fault occurs at the active board, the standby board has only to take over the controlling authority from the active board to complete duplex switching operation.
However, unlike the 2G mobile communication system, 2.5G and 3G mobile communication systems use a processor having faster performance speed than that used in the 2G mobile communication system. Therefore, a high-speed processor having upgraded kinds of Central Processing Unit (CPC) and clock speed is used. Accordingly, this system can be sensitive to noise at the time of transmitting data and a fault can occur at the time of reading/writing a memory. Consequently, the concurrent writing method is not appropriate for use in 2.5G or 3G mobile communication systems.
The above references are incorporated by reference herein where appropriate for appropriate teachings of additional or alternative details, features and/or technical background.